a simple circuit

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A voltage accross a resistor. That's as simple as they come.

You fool, you forgot a voltage across absolutely nothing!

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You dolts, you forgot the even simpler circuit !

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Wave it in a magnetic field ! Watch that induction happen !

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And the simplest of them all, contained in the following line:

 

 

It is impressive how some people go for complexity any change they get. And bitter_engineer, down there, just does not get it: you don't have to wave it in a magnetic field. It can just sit there and be ... simple.

You are all wrong.

bob the cow is wrong because every medium across which voltage can be induced has some resistance, even if it is infintesimal. Remember: V=iR, by definition.

baffo is wrong because the mechanism to change the magnetic field can be modelled as a voltage source, reducing it to StormHunter's example.

StormHunter's example is correct for almost every instance you can see in The Real World, but one can induce a current in a loop of superconducting material, then remove the transient and let it run indefinitely, or until you perturb its magnetic field. R=0, so V=0.

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